Due to increased terrorist activity, there is a need for practical and high resolution gamma and neutron radiation detectors which can detect radioactive “dirty bombs” and other sources of radiation. Further, hand held or portable devices including for example, Hand Held Radioisotope Identification Devices (HHRIID's) are in high demand. Newer standards such as ANSI N42.33 (Type I) and ANSI N42.34 have also been specified due to the increased performance demands.
The typical approaches to gamma-radiation spectroscopy utilize NaI, CsI, Cadmium Zinc Telluride (CZT), Bismuth Germanate (BGO) or High Purity (HP) Germanium as direct-detection or scintillator materials. A desirable radiation detector able to simultaneously detect gamma- and neutron-radiation should demonstrate improved functionality and identification performance, i.e., it should be able to distinguish if suspect radiation is Naturally Occuring Radioactive Materials (NORM), Special Nuclear Materials (SNM), Medical, Industrial isotope or combination thereof, be easily deployable, and have low total cost of ownership.
Improved identification performance relies heavily on energy resolution, for which a HP Ge based detector would have nearly ideal characteristics. However, the need for cryogenic cooling, and materials cost in this type of detector severely impacts functionality, deployment, and total cost of ownership. Other materials solutions such as NaI, CsI(TI) or (Na), or CZT suffer from low energy resolution, high price, or inability to obtain sufficiently large volumes, which will also preclude meeting the above mentioned requirements and/or U.S. Homeland Security requirements for HHIRID's.
The problem has generally been addressed by separating the gamma and neutron components into two separate detector materials. Most of the existent combinations of simultaneous gamma and neutron detection use materials combinations that do not allow adequate identification, are not easily deployable, and/or have high total cost of ownership.
Thus, a high-resolution combined neutron and gamma radiation detector that helps to address at least some of the concerns above is needed.